A Queens judge ripped into a father who shook his baby son to death, calling the crime “monstrous” and then sentencing the dad to 18 years in prison.

“You should have been a father to him,” Queens Supreme Court Justice Richard Buchter scolded Saul Cortez.

Cortez, 25, of Arverne, was left alone for 20 minutes with his 8-month-old son, Mario Patrice, on April 5, 2010, when he became frustrated and angry with the baby’s crying and repeatedly shook and punched the infant in the back, according to a criminal complaint.

The child’s mother, Monica Patrice, refused to attend the sentencing because of her “fear and anxiety” over losing her child at the hands of his father. But in a statement submitted to the court, she said she wishes he could get the “electric chair.”

Cortez pleaded guilty last month to the manslaughter and assault of his son. He faces deportation to Mexico upon completion of his sentence.